The official reasons for Ms. Hartson’s termination, two people familiar with it said, were mundane. But she told associates that she believed she’d been fired for her politics. In a Zoom meeting with employees on Jan. 26, the chief executive of Hachette Book Group, Michael Pietsch, and Daisy Hutton, the executive who oversees Center Street, didn’t mention Ms. Hartson. But they reassured employees that they had learned the lessons of the Capitol siege of Jan. 6: no hate speech, no incitement to violence, no false narratives. And they’ve separately made clear to both editors and agents that they’re shifting back toward think tank conservatives, and away from fire-breathing politicians. (Ms. Hartson didn’t respond to questions about her views and her firing.)

“The conservative movement is in a state of flux, and the next few years will be a particularly rich time for conversation about the future of conservatism in America,” Ms. Hutton, who is based in Nashville and whose background is primarily in Christian publishing, said in an email. “Center Street will continue to publish thoughtful, provocative, lively and informative books that contribute meaningfully to the shaping of that conversation.”

Hachette is hardly the only mainstream publisher steering away from MAGA books.